COD-bearing organic compounds must be eliminated in the electroless plating solution, and electrical oxidation is used to reduce high COD concentrations. Removal efficiency greatly decreases at low COD concentrations, which has led to the treatment of low COD concentrations by UV light irradiation.
COD was removed in the following sequence: ultralow→low→high-pressure mercury lamps. Efficiency is increased by adding ferrous or ferric ions to the treated solution. The removal rate is even further improved by treatment using hydrogen peroxide in combination with ultraviolet-ray exposure.